Existing transport refrigeration systems are used to cool containers, trailers, and other similar transport units (typically referred to as a “reefer”). Modern reefers may be efficiently stacked for shipment by ship or rail. Typically, when reefers are shipped by truck, a single reefer is placed on a trailer chassis. When cargo in the container includes perishable products (e.g., food product, flowers, etc.), the temperature of the reefer must be controlled to reduce loss of the cargo during shipment.